The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft is driven by several turbojet engines each housed in a nacelle accommodating an assembly of auxiliary actuating devices linked to its operation and providing various functions when the turbojet engine is in operation or stopped.
These auxiliary actuating devices comprise in particular a mechanical thrust reverser system.
A turbojet engine nacelle generally has a substantially tubular structure comprising an air inlet upstream of the turbojet engine, a median section intended to surround a fan of said turbojet engine, a downstream section intended to surround the combustion chamber of the turbojet engine and optionally integrating thrust reversal means, and is generally ended with an ejection nozzle whose outlet is located downstream of the turbojet engine.
The modern nacelles are intended to accommodate a bypass turbojet engine capable of generating, by means of the blades of the rotating fan, a hot air flow (primary flow) and a cold air flow (secondary flow) which circulates outside the turbojet engine through an annular passage, also called flow path, formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two air flows are ejected from the turbojet engine through the rear of the nacelle.
The role of a thrust reverser is, during the landing of an aircraft, to improve the braking capacity of the latter by redirecting forward at least part of the air ejected from the turbojet engine. In this phase, the thrust reverser obstructs at least one portion of the flow path of the cold flow and directs this flow to the front of the nacelle, thereby generating a counter-thrust which is added to the braking of the wheels and air brakes of the aircraft.
In general, the structure of a thrust reverser comprises a thrust reverser cowl displaceable between, on the one hand, a reverse jet position in which it opens into the nacelle a passage intended for the diverted air flow and, on the other hand, a direct jet position in which it closes this passage.
In the case of a thrust reverser with cascade vanes, the reorientation of the air flow is carried out by cascade vanes, associated with thrust reverser flaps blocking at least partially the air flow path, the cowl having only a simple sliding function aimed at discovering or covering these cascade vanes.
The thrust reverser flaps, also called blocking flaps are, in turn, activated and driven by the sliding of the movable cowl until at least partially obstructing the flow path downstream of the cascades, so as to improve the reorientation of the cold air flow.
In a known manner, the cascade vanes are mounted on a front frame serving as a fixed portion of the thrust reverser device and attached to a casing of the fan of the turbojet engine. This front frame also provides the support of cylinders for actuating the movable cowls.
Apart from participating in a thrust reversal function, a movable thrust reverser cowl, through its belonging to the rear section of the nacelle, includes de facto a downstream portion forming the ejection nozzle.
The section of the ejection nozzle can be adapted according to the different flight phases, namely take-off, climb, cruise, descent and landing in order to maintain a desired section of nozzle depending on the regime of the turbojet engine. The nozzle will then be called a variable nozzle.
Such a variable nozzle is associated with an actuating system allowing this variation of section.
There are several solutions for carrying out a variable nozzle.
A first solution is to provide for pivoting end flaps mounted on the movable thrust reverser cowl and whose pivoting results in an increase or a reduction in the outlet section. Such a system is described, in particular, in the document FR 2 929 998.
There are also known panels mounted movable in translation inside the movable thrust reverser cowl, in a telescopic manner, whose recoil or retraction similarly causes the increase or the reduction of the outlet section.
In the context of a thrust reverser provided with a variable-section nozzle, it is known to actuate the deployment of the movable cowl and the mechanism for varying the section of the variable nozzle by the same cylinders, the movable cowl and the variable nozzle being coupled and uncoupled by a coupling device.
This coupling device selectively links the cowl and the variable nozzle in a rigid manner, the variable nozzle being free when the cowl is locked on the structure of the thrust reverser in its direct jet position and the variable nozzle being coupled on the cowl when the cowl is unlocked, so that the nozzle and the cowl are simultaneously driven in displacement.
This type of coupling device is generally relatively complex, it often requires an alignment of different parts to allow the coupling of the cowl and of the variable nozzle.
The high number of parts of this type of coupling device is a source of failure and often leads to an average reliability.
In addition, the coupling and uncoupling jolts are not damped and can lead to stresses which are detrimental in terms of wear and reliability of the mechanical parts.